1. Field of the Invention
This invention relates to lubricant seals for rotary shafts, more particularly to an improved seal suitable for use in applications such as railway car journal bearings for retaining the lubrication in the bearing and for excluding dust and other contaminants from the bearing.
2. Description of the Prior Art
Roller bearing assemblies incorporating two rows of tapered roller bearings supported between opposed concentric races in a self-contained, pre-lubricated, sealed package for mounting onto journals at the ends of axles or shafts are well known and widely used, for example, as rail car bearings, and the present invention will be described with reference to such rail car bearings, and to seal assemblies for use in connection with such bearings, it being understood that the improved seals according to the present invention may be employed in sealed lubricated bearing assemblies of various configurations and for various uses.
Lubricant seals employed between a shaft and a cylindrical housing within which the shaft is supported for rotation by antifriction bearings frequently consist of a rigid support ring adapted to fit in fluid-tight relation within a cylindrical bore in the housing and to support a resilient elastomeric or rubber-like sealing element in fluid-tight contact with the outer cylindrical surface of the relatively rotating shaft, or with a cylindrical surface on a wear ring, bearing cone or other member supported on the shaft. When seals of this type are operated in an environment such as on a railway car axle where foreign matter such as dust, mud or water may tend to enter the bearing cavity, it is common practice to employ a secondary seal, generally referred to as a dust seal, to prevent ingress of such material (dust) into the bearing. Seal assemblies of this type are illustrated, for example, in U.S. Pat. Nos. 5,186,548 and 5,551,886.
As pointed out in the above-mentioned U.S. Pat. No. 5,186,548, continuous contact between an elastomeric seal and a rotating rail car axle can produce friction which in heavy contact seals has been known to contribute to overheating of the seal and breakdown of the lubricant. Further, seal friction may result in rolling resistance, particularly when starting a car from the rest position and when operating at low speeds. Recent improvements in railroad sealing and lubricating technology have lessened the rolling resistance and temperature effects of seals, but the industry continues to devote substantial research, effort and resources to produce a more effective and efficient seal.
It is also known to provide labyrinth-type seals for bearings supporting a shaft in a housing and examples of such seals may be found, for example, in U.S. Pat. Nos. 2,014,859; 3,198,318; 3,679,277 and 5,259,628. Such seals frequently are employed in connection with stationary equipment such as pillow blocks for motors or for conveyor rollers where access is readily available for frequent lubrication so that loss of some lubricant is not critical, or where the bearing is not subjected to extremely heavy dynamic loads which may subject the shaft to bending and consequent misalignment of the intermeshing labyrinth elements. Note, for example, U.S. Pat. No. 2,014,859 wherein helical grooves are formed on the labyrinth elements to intentionally product a pumping action deliberately pumping some lubricant from the sealed bearing to expel dust particles which may tend to migrate into the sealed area. Labyrinth seals are also frequently employed as secondary, or dust seals in combination with a resilient primary seal, but such seals generally have not been considered for application to rail car journal bearings.
The term "labyrinth" has also been employed to describe rail car bearing seals in which one or more resilient lips are spaced closely to a relatively rotating smooth surface such as a cylindrical shaft or wear ring surface on a radially extending rigid support ring element. Such seals have not provided a tortuous path for the lubricant as is generally required for a true labyrinth seal, however, and are not believed to be properly termed labyrinth seals. Examples of such seals are disclosed, for example, in U.S. Pat. Nos. 4,819,949; 4,770,548; 4,770,424; and 3,628,837.
It is, therefore, a primary object of the present invention to provide an improved bearing shaft seal assembly.
Another object is to provide a shaft seal suitable for use in connection with a railway car journal bearing or other dynamically loaded heavy duty bearing, and which employs a primary seal in the form of a labyrinth comprising a plurality of closely spaced concentric cylindrical surfaces and a secondary or dust seal spaced outboard relative to the bearing from the primary labyrinth seal.
It is another object of the invention to provide an improved rail car journal bearing seal including a labyrinth-type primary seal in combination with a resilient dust seal in contact with a cylindrical surface on the rotating axle.
Another object of the invention is to provide an improved wheel bearing seal assembly for heavy duty vehicles having improved sealing qualities and longer service life.
Another object is to provide such an improved rail car journal bearing seal assembly which produces lower rolling resistance and which operates at a cooler temperature than conventional seal assemblies.